Tranny Noise

[Phantomiata]

Hi All.

I took my 944 into the mechanic for state inspection and asked about the metallic grinding noise coming from the transmission. He drove it and said it was the bearings in the transmission.

He seemed unphased by it and when I asked him if it meant the transmission was facing imminent failure he said probably not. He said I could get quite a bit more life out of it, but it's hard to know with a transmission with 155,000 miles.

Anyone have a transmission with noisy bearings? How much life did you get out of it? The car is my daily driver and I take it on long trips. What's the failure mode for bearings, do they just keep getting louder? Does the transmission just eventually "lockup"?

Thanks for any insights.

[adrian jaye]

tranny noises are very weird.

let me give you 2 pieces of info

1> check that you have the correct grade and ammount of oil in the tranny, if your not sure, drain it and refill it

2> a common noise caused by the 5th gear idler wheel, causes a grinding/rumbling noise, its a well known problem and only occurs when the car is warm, if so, it wont fail, and has been knon not to cause any problems

HTH

Ade

[Phantomiata]

I did replace the fluid. It looked a little dirty, but I didn't find any metal shavings or anything like that. It didn't make a difference in the noise.

I hadn't heard of the 5th gear idler wheel. The intensity of the noise varies with load on the transmission. The noise is loudest when you release the throttle with the car still in gear, second loudest when accelerating and quietest when cruising at a steady speed. The noise is constant and happens when the car is cold.

Thanks for the thoughts.

[Rmills944]

Is the noise like a grinding or a metallic howling?
A metallic howling is what happened to mine before I got the tranny/clutch failure because of the rubber disc.
A grinding could also be the cat hitting the torque tube - that would be easy to fix - just bend a flange on the cat away from the torque tube. When that happened, it was fairly loud and sounded like it was coming from the back.

[Phantomiata]

My noise is more of a grinding. The clutch was replaced 5,000 miles ago.

Hmm. I hadn't thought of a heat shield rubbing the torque tube. The noise started after the clutch was replaced, so I guess it's a possibility. I will check it out.

Thanks.

[tifosiman]

It may not be bearing noise.

At 155K, I would be willing to bet the tolerance between the ring and pinion gears has increased due to wear. The factory actually recommended opening up the trans and checking the tolerance levels at certain mileage intervals, and adding shims if necessary, to tighten things up. Most 944's have not had this maintenence done.

What eventually happens is the tolerance increases to the point where some teeth get cracked and broken off on either the ring or pinion gear (because the load is no longer spread properly). Then catastophic failure happens when the pinion gear hits that "dead spot" where the broken teeth are and spins and smacks into the next good teeth, resulting in shear of several more teeth and making it unusable. It won't lock up when it breaks, it will more than likely just no longer let you go anywhere because the output shaft is no longer making contact with the differential.

You could spend the money to have a transmission place crack open your trans and work on it ($$$), or just continue to drive it until it breaks and then spend $500 or so on another used one. Most people do the latter.

The future life of your noisy trans will have an inverse proportional relationship to the number of hard launches and power shifts that you make.

Hope that helps!

[Phantomiata]

Thanks for the info.

My suspicion is that it's the r & p as well, but the mechanic says otherwise. I guess it doesn't make a difference; the transmission is on its way out.

The suggestion about taking it is easy is good advice. I've been babying it since the noise started six months ago.

[adrian jaye]

Originally posted by Phantomiata
I hadn't heard of the 5th gear idler wheel. The intensity of the noise varies with load on the transmission. The noise is loudest when you release the throttle with the car still in gear, second loudest when accelerating and quietest when cruising at a steady speed. The noise is constant and happens when the car is cold.

the 5th gear idler is only noisy when in neutral and in idle

cheers

A

[Zero10]

Mine's had that noise on deceleration since I bought it. 40,000km's later, it hasn't changed significantly. If it's bearings, it will only get louder, and eventually you might experience some kind of transmission failure, I'm not sure exactly what would happen if the bearings ground right out.

Tifo, good to know that I can shim the R&P to help prevent the dreaded failure.
I had always considered it, and in the back of my head, I thought the nature of the failure was an incorrect free play adjustment, due to wear. Nice to have somebody confirm that.

Perhaps over the winter, I will be replacing my syncro's. Do most places that carry the syncro's carry the shims for the R&P?

[tifosiman]

Originally posted by Zero10


Perhaps over the winter, I will be replacing my syncro's. Do most places that carry the syncro's carry the shims for the R&P?

Hopefully you have all of the factory tools needed and a shop press, because that's what's entailed in replacing synchros on the 944 trans. It's rather tool-intensive. If you wait until the spring next year, I will be able to do it for you (but I digress).

I know that your local Porsche Dealer can still get the shims, they have part#'s. There are many different part#'s based on shim thickness. Since they have part#'s, that also means that you could just call or email Sunset and have them ship what you need.

IIRC, there is also a part# for a kit that has an assortment.

Adding more shims requires less tools than the synchros, but is a bit trickier to get *just right*. The factory service manual has a good write up on this.

[Zero10]

Hmm, my experience with transmissions is as follows:
I've changed and rebuilt several differentials on cars where it is not part of the transmission (RWD cars with transmission in the front), as well as rebuilt the entire transmission on my subaru (FWD). The one on my subaru was so simple that a monkey could have done it, and it was rebuilt without the aid of any special tools.
I've shimmed other differentials before, and that is why I originally suspected that perhaps this was the nature of the R&P failure in our cars. I never had much trouble with them, but you're right, sometimes it is rather tricky to get just right. It's probably a lot worse with an integral differential, instead of a seperate one.

Now, I do have a 20 ton hydraulic press, and most every tool a normal mechanic's shop would have. I understand some rather large wrenches are required for a transmission overhaul, but I am not aware of any other tools. Could you perhaps enlighten me on what else I might need?

I had a thought, (I know, one whole thought!), if our R&P is the same as in an audi 5000 series, perhaps a local transmission shop might have the shims? They are probably a standard size.

Hmm, you would rebuild it for me? I can pay you in beer, but unfortunately, Ohio is a little far for me to travel =)

[tifosiman]

Originally posted by Zero10
Hmm, my experience with transmissions is as follows:
I've changed and rebuilt several differentials on cars where it is not part of the transmission (RWD cars with transmission in the front), as well as rebuilt the entire transmission on my subaru (FWD). The one on my subaru was so simple that a monkey could have done it, and it was rebuilt without the aid of any special tools.
I've shimmed other differentials before, and that is why I originally suspected that perhaps this was the nature of the R&P failure in our cars. I never had much trouble with them, but you're right, sometimes it is rather tricky to get just right. It's probably a lot worse with an integral differential, instead of a seperate one.

Now, I do have a 20 ton hydraulic press, and most every tool a normal mechanic's shop would have. I understand some rather large wrenches are required for a transmission overhaul, but I am not aware of any other tools. Could you perhaps enlighten me on what else I might need?

I had a thought, (I know, one whole thought!), if our R&P is the same as in an audi 5000 series, perhaps a local transmission shop might have the shims? They are probably a standard size.

Hmm, you would rebuild it for me? I can pay you in beer, but unfortunately, Ohio is a little far for me to travel =)

Sounds like you are more than handi-capable enough to handle the task then. I just ordered a 20-ton press myself.

If you have the factory manuals, take a look at the section on transmission rebuilding. In that section, there are pages that have photos and part#'s of the tools needed for the job. Off the top of my head, there are drifts, separators, specific press plates (you could fab these), sleeves, gear pullers (easy), and feeler gauges (easy). The hard to find tools are going to be the specific drifts and sleeves. Most of the ones with VW part#'s are NLA, I have been looking for those myself. Most of the ones that are Kukko tools are available and/or can be cross-referenced with other manufacturers.

You are correct, some of the audi models used the 016 gear boxes, but with different r&p ratios. If you find a cheaper source for the shims in their audi guise, let me know. I have accessed a Russian webpage that has audi part#'s for the diffs and some other trans parts, but I haven't spent enough time on it to find the shims to check the part numbers.

[tifosiman]

Wanted to add the pic below of the 016 944 trans opened up so you see one the synchros on the input shaft. Dis-assembly and getting to that shaft is not too bad, it the work of pressing off the gears and synchros that is the meat of the issue and thus the need for the tools.



I forgot to mention, while you have it apart, that would be a good time to use the procedure in the manual to check for the proper shim thickness and take care of that.

Man, check out that shredded pinion gear! That was a bad day at the autocross, only happened on my 3rd run of the day.

[Zero10]

Syncro's look good =)

Hehehe, anyhoo, I am a little worried about the whole pre-load issue, the gear box is quite different inside than the one in my subaru, but I think I'll get through it.

Do you happen to know the ratio's on the audi gear-boxes, and if their R&P's will fit? I'm considering a diesel swap, and I need to reduce the output gearing by 2/3, so my 4000rpm red-line will be like a 6000rpm red-line, and I can still go 200kph if I want to.
The diesel swap is still in the works, but my birthday is coming up, perhaps I will get a 1.9L TDI or a 2.5L TDI for my birthday?...

[tifosiman]

From the list that I have been poking thru to cross-reference stuff, there are two audis that definetly have interchangable parts with our cars.

1985-87 Audi 80/90 quattro has the same diff design that the 944 trans does. The Porsche ratio is 9:35, while the audi 80/90 has two:

"016 409 143 AP" is 9:37
"016 409 143 AK" is 9:41

Also, the Audi 1985-87 100/Avant quattro has a diff that interchanges with ours, it is available in the following ratios:

"016 409 143 AP" is 9:37
"016 409 143 AN" is 9:43 (Gesh, low gears..Mmm)
"016 409 143 AR" is 9:37

Hope that helps and doesn't add more confusion...

[Zero10]

Let me make sure I have the numbers straight in my head, that's pinion teeth:ring teeth, correct?
I always see them expressed as a number, instead of a ratio, i.e. 4.10.
Seems like all of those ratio's work against me, that really sucks.
Looks like I might have to source a R&P from a local shop or something...
I think around a 9:27 would be perfect, maybe a 9:25

[bryanthompson]

I really really want to get my hands on a crapped out 944 trans, then learn how to rebuild it... It'd be good to have a backup, but I'm more interested in knowing how to do it, that looks awesome!